1. Field of the Invention
The present invention relates to a laser mass spectroscopic analyzer for mass spectroscopic analysis of ions separated from solids or liquids and more particularly to a laser mass spectroscopic analyzer and method capable of analyzing a sample located outside a vacuum vessel.
2. Description of the Prior Art
FIG. 13 is a schematic construction diagram of a conventional laser microprobe mass spectroscopic analyzer shown, for example, in Japanese Patent Laid-Open Application No. 66245/1983, in which the reference numeral 1 denotes a vacuum vessel; numeral 2 denotes a sample placed within the vacuum vessel 1; numeral 3 denotes a laser beam emitted from a laser device 4; numeral 5 denotes a focusing lens for focusing the laser beam 3 into a fine spot; numeral 6 denotes a window (e.g. glass window) for conducting the laser beam 3 into the vacuum vessel 1; numeral 7 denotes secondary particles such as ions and neutral particles (atoms and molecules) generated by the radiation of laser onto the surface of the sample 2; numeral 8 denotes a mass spectrograph for mass spectrometric analysis of ions; and numeral 9 denotes a sample inching device for inching the sample to conform the portion to be analyzed to a focused spot of the laser beam.
The operation of such conventional analyzer will be described below.
The laser beam 3 emitted from the laser device 4 passes through the window 6 attached to the vacuum vessel 1 and is conducted into the same vessel, in which the beam is focused as a fine spot on the surface of the sample 2 placed within the vacuum vessel. By this focused radiation of the laser beam 3 the secondary particles 7 such as neutral particles, e.g. atoms and molecules, electrons and ions (charged particles) are emitted from a very small region on the surface of the sample 2. Among the secondary particles 7, ions as charged particles are introduced into the mass spectrograph 8 for mass spectrometric analysis, whereby there are performed elementary analysis and structural analysis for the very small region of the sample 2. Since the average free stroke of ions is smaller than 1 .mu.m in the air, ions are scattered and their electric charge lost by impingement against gas molecules, etc. To avoid this, the mass spectrometric analysis in this conventional apparatus premises that the sample 2 should be placed in vacuum.
In the conventional laser mass spectrometric analyzer constructed as above, sampling and ionization of the sample 2 are performed at a time by a single radiation of laser beam, so it is necessary to place the sample 2 within the vacuum vessel 1 in which is disposed the mass spectrograph, and for controlling the position of the sample 2 located in the vacuum vessel 1 it is necessary to use a special manipulator (goniostage) for vacuum as the supporting device 9, resulting in a high equipment cost. Moreover, the size of the sample 2 is restricted by the size of the vacuum vessel 1, and a liquid sample or a sample having a high vapor pressure is impossible or difficult to analyze. Further, it has been impossible to analyze living things alive in vacuum. Additionally, at the time of change of sample it is necessary to release the vacuum and the sample changing time becomes longer because of vacuum exhaustion.
The present invention has been accomplished for solving the above-mentioned problems and provides a laser mass spectrometric analyzer capable of analyzing a sample placed outside a vacuum vessel.